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CROSS Safety Report

New basements beneath existing properties

Report ID: 297 Published: 1 April 2013 Region: CROSS-UK

This report is over 2 years old

Please be aware that it might contain information that is no longer up to date. We keep all reports available for historic reference and as learning aids.


A reporter is concerned about the construction of some basements in London.

Key Learning Outcomes

For civil and structural design engineers:

  • The condition and stability of adjoining structures should be determined to make sure that the methodology of basement installation does not endanger the stability of adjoining property

  • All possible load conditions ought to be considered which includes surcharge from adjoining properties

For homeowners and builders:

  • The design of basements should be carried out by a suitably qualified and experienced engineer

Full Report

Find out more about the Full Report

The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.


A reporter is concerned about the construction of some basements in London. They reviewed two projects covering basement works in relation to building regulation checks on the structural aspects.

The following characteristics were seen by the reporter:

  • They were probably two projects with the least percentage of costs spent on architectural and structural design that they have come across in three decades of practice
  • There was a definite danger to the builder, based on the submitted designs
  • They were very likely to cause major problems for the neighbours
  • It was suspected that the works would be outside the competency of all parties, and this included the client and the Building Inspector

After the reporter, acting as a building regulation’s checker, expressed concern they said that the projects were passed to another engineer.

Expert Panel Comments

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Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.

The increase in major or complex basement constructions in London in particular is a concern as the implications do not always appear to be appreciated by those involved. Such projects may not be ‘building works’ but ‘construction projects’, with an attendant necessary increase in competency.

Indeed, it has also been reported that in London basements under terraced houses are being constructed without any engineering input and no regard to the Party Wall Act, ground water movement, or the effect on neighbouring dwellings.

Danger during construction is beyond the scope of building control but it is essential that this is considered during the process. There are usually understandings between building control and the Health and Safety Executive (HSE) such that once a project gets underway on site unsafe actions are referred to HSE. The aim however should be to intercept these projects prior to construction and perhaps this report reinforces the need for licensing certain types of work.

It is to be hoped that available guidance would be consulted, or competent specialists brought in as required. Competency of those in the chain of responsibility is very important and features in many reports to CROSS about failures. Basements for dwellings from the Basement Information Centre gives general advice and is soon to be up updated.

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